[Radiance-general] multiprocessor systems, Radiance, and you

[Rob Guglielmetti]

Jack de Valpine wrote:
 > Hi All:
 >
 > I know that I am about a week behind on this topic
<snip>

Hi Jack.  Thanks for weighing in.  (and thanks to the others who had
input late last week.)  And yeah Jack, I know all about the weather
you're having, because we're having some of your Boston-style cold down
here in NYC today.  Brrrrrrr!

 > For running parallel rpiece type jobs without complications of network
 > related issues (i.e. NFS and others) smp boxes are a must have depending
 > on the rendering task complexity...

 > Now, since Rob is running lots of rtrace jobs, the problem that he is
 > facing is more likely management and batch processing of multiple
 > "rendering" jobs.

Yes.  As usual, my questions seem rather stupid immediately *after* I
ask them.  Absolutely right, mine is a process management problem and
could be solved just as easily with intelligent scripting over two
machines, there's no inherent gain to a dual box except that for one
software installation I essentially have two cpus available for
rtrace(s), and of course it's a cheaper way to have two cpus.  I should
note at this time that the RedHat installer is busily copying files to
the new computer as I type this.  I ended up going with a single,
primarily for financial reasons.  But I do appreciate all the info and
advice everyone gave me on this list.  Further to that:

While it is not clear exactly what the task is, my
 > guess would be that there are lots of rtrace jobs representing some kind
 > of timeslice analysis that need to be started and then on completion the
 > resulting data must be integrated or aggregated for evaluation and
 > presentation. This really is a scripting task at its heart, where the
 > repetitive tasks need to be understood and scripted accordingly. It
 > should not really matter what scripting/programming tool (bash, perl,
 > python, C), whatever you are most comfortable with. Rob, if you can,
 > maybe you can give us a better understanding of the "rendering"
 > production task you are facing, people maybe able to give you feedback
 > on other scripting ideas than what you have already put together.

Yes, it's rather like the directions on the shampoo bottle:  lather,
rinse, repeat.  Except in my case, it's rtrace (optionally performing
some low-resolution rpicts too), increment hour, repeat.

Right now I'm using a modified version of the time-of-day image sequence
shell script that John Mardaljavec wrote and published in "rendering
with Radiance".  Mine uses rad instead of calling the rpict directly (at
least when I do renderings).  It's still quite basic, but I hope to work
on it some more soon.  Basically I set up a rif file the way I want it,
and have a file of calculation points for rtrace.  Then I set the
variables in the shell script for the particular run (June 21/clear sky
or Dec 21/overcast sky, etc), and it's off to the races.  If I ask for
renderings, the script calls rad and renders an image as well, putting
titles on it based on the variables, and "pcond-ing" it too.  The data
from rtrace gets "lam-ed" to the previous hour's data.  Then the process
loops around again:  gensky creates a new sky for the next time
increment, sed modifies the rif file with new filename prefixes (so we
can keep track of everything later), and we go again.  I wanna add stuff
like report building, graph generation with gnuplot or somesuch, and a
host of other things, but my application for the 36 hour day is
apparently still held up in processing. =8-)

It's just the sheer number of simulations, and high number of ambient
bounces that had me looking toward a dual cpu machine.  I see now that I
*could* still put a dual box to good use (through scripting), but in the
end economics decided the road I was to travel.  Like I said before, if
I now buy a second single-cpu box, I essentially have the same
functionality (to me) as a dual box, and I gain redundancy, for just a
few more bucks.

Maybe someday I'll need the dual for rpiece, but right now my models are
pretty basic and I'm doing more with numbers than pixels, so...

P.S.
RHL8 install complete, installer didn't find my NIC.  Sigh.  So close...

----

      Rob Guglielmetti

e. rpg@rumblestrip.org
w. www.rumblestrip.org